Not everyone can live in Maine, and we consider ourselves fortunate to be among the few. 

Among the experienced contractors, I'd bet you can't find a single one.All that said, this is your decision. 

We have the same situation...we took last year's utility bills, split them among the three units, and added them to market rate rents. 

The income after guaranteed payment is taken out will be split among the remaining 3 partners based upon the agreed upon profit/loss percentages.

Sounds like ultimately it will come to what the HVAC specialists recommend and the cost differences among the options.  

Among the "magic words" you mentioned include, "... and we have a video of that too. 

This is especially true of how the self-made among the affluent, those who built their fortunes from scratch, started.

Nothing appeals to everyone, however among the following, my wife and I have a strong preference over the personal  'yuck' factor in of the other. 

There’s a video of the mourners fleeing the area, scattering among the tombstones. 

You can also look at each of your AirBnB 'comps' in your area and see if there is a commonality among the property 'hosts' or 'co-hosts', and if there is, I'd suggest you reach out to that person to learn more about your local market.